Mechanical pipette



www@ S. ggfs G. S. RIGGS MECHANICAL PIPETTE Filed Nov. 14, 1947 f/A, fill/IV ff NW, m, w@

A fio rneys Patented Nov. 21, 1950 f MECHANICAL PIPETTE George S. Riggs, Salinas, Calif., assignor of onethird to Carl A. Nisson and one-third to Samuel C. Riggs, Salinas, Calif.

Application November 14, 1947, Serial No. 785,977

3 Claims.

The present invention relates to certain new and useful improvements in what is believed to be a practical and readily adaptable pipette, of a mechanical type, which is especially, but not necessarily, adapted for use by milk inspectors during the period of testing for bacteria which may be present in the milk.

It is a matter of common knowledge in the trade that the pipette now and customarily used by milk inspectors comprises a glass tube which is about .018 in diameter and has suitable graduations to measure the amount of milk taken in through the intake hole at the inlet end. The inspector puts the tube in his mouth andby suction charges it full of milk up to the capacity mark or graduation and then blows it out again on a slide. In addition, he will usually pick up another suitable instrument to spread the sample of milk on the slide before it is placed under the microscope and since samples are taken every thirty seconds or so it can be seen that the time element and other diiculties are encountered and involved. AWhat is more important, bacteria laden samples are hazardous to the health of inspectors.

The object of the present invention is to provide a sample taking pipette of a wholly mechanical type which is simple, practical and adequate in attaining the desired ends.

Briefly, the preferred embodiment of the invention is characterized by a barrel constituting the sample receiving and measuring cylinder, said barrel having a suitably bored intake tip at the inlet end, and being provided with a spring returned manually depressed plunger which is such as to expedite the steps of rst sucking the milk, and secondly, expunging it for deposit on the aforementioned microscope slide.

Other objects and advantages of the invention will become more readily apparent from the following description and the accompanying illustrative drawings.

In the drawings, wherein like numerals are employed to designate like parts throughout the views: y

Figure 1 is a view partly in section and partly in elevation of a milk sample taking and measuring pipette constructed in accordance with the principles of the invention.

Figure 2 is an elevational view of same showing the plunger projecting beyond the intake tip.

Figure 3 is a top plan view of the structure seen in Figures 1 and 2.

Figure 4 is a cross-section on the line 4-4 of Figure 1, looking in the direction of the arrows.

Reference being had to the structure, better detailed in Figure 1, it will be seen that the barrel, which is of appropriate material, preferably transparent, is denoted by the numeral 6 and this constitutes an appropriate cylinder. It is internally screw-threaded at its upper as at 'I and also internally screw-threaded at the lower end, as at 8. At the upper end I provide integral outstanding finger grips 9. Also there is a bushing I which is threaded into the screw-threads II, said bushing having a knurled finger grip Il and there being a nut lock provided at I2 to retain the bushing in set positions.

The plunger, including a rod I3, is operable through the bushing and the outer end portion of the rod is provided with a finger piece or depressor I4. A shoulder I5 on the intermediate portion and in the cylinder provides a stop and is engageable with the adjustable bushing, the latter serving as a regulatory shoulder. The inner end portion I6 carries a reduced portion I'I which is in effect a piston.

Reference is had now to the nozzle-like tip I8 which has its screw-.threaded shank I9 screwed into the screw-threaded portion 8 and has its iiange portion 20 Iabutting the end of the cylinder. The outer end of the tip is appropriately reduced as at 2| and the entire tip is formed with a bore constituting an intake and discharge passage 22. The aforementioned piston I1 has tight sliding lit in said passage. A neck-like extension 23 on the inner end of the tip and located in the cylinder provides a stuing box and has a centrally apertured closing nut 24 for the piston and said nut serves to hold in place the desired kind of packing material as at 25. Attention comes now to a coiled spring 26 which is situated in the cylinder, one end thereof surrounding the piston rod and `bearing against the stop shoulder I5, the other end surrounding the stufng box and bearing against the screwthreaded attaching stud or body I9.

In practice, the device is handled like a plungerequipped syringe. That is to say, two fingers, rst and second, for example, straddle the barrel beneath and grip around the hand grips 9 and the thumb is placed on the thumb piece I4, whereupon the plunger is forced into the cylinder against the tension of the spring. This operates the piston rod I1 through and beyond the bore 22 and it takes the projecting position seen in Figure 2. When the plunger is released, sufficient suction is created that whenr the nozzle is inserted into a container of milk, a nominal amount of milk is sucked into the passage or bore 22 which at that time becomes a measuring chamber. Then, by forcing the plunger in the opposite direction, the trapped sample of milk is expunged and may be thus squirted on the aforementioned microscope slide (not shown). It is to be mentioned that when the piston element l1 is projected to the protruding position seen in Figure 2, said projecting end portion may be used as a sort of a brush or spreader. That is to say, the so-called brush may be used for spreading the milk around on the slide for better microscopic study work.

The construction and operation will be clear, it is submitted, from studied consideration of the specication, drawings --and accompanying claims. Therefore, a more extended description is deemed to be unnecessary.

Minor changes in shape, size and rearrangement of parts may be resorted to in actual practice so long as they do not depart from the spirit of the invention nor the scope offfthe accompanying claims.

Having described the invention, what is claimed as new is:

1. A mechanical pipette for taking milk samples for testing purposes comprising abarrel open and internally screw threaded .at opposite ends, said barrel being provided at one end with outstanding iinger-grips, a screw-threaded bushing adjustably screwed into said one end, a screwthreaded centrally bored nozzle-tip screwed into the opposite end of said barrel, the bore in said nozzle-tip being relatively restricted and linearly straight from'end to end and constituting a milk receiving and .storing chamber of predetermined and'limited capacity and being adapted to permit a limited amount of milk to be sucked vinto same and subsequently discharged on a microscopic slide for testing purposes, a plunger including a relatively large rod portion slidable in said bushing, said rodportion having a shoulder yabutting said bushing so that the bushing and shoulder portion of the plunger may be adjusted in respect to the-barrel, said plunger also including a reduced lrod constituting a piston and tting and operating snugly in the bore in said nozzle tip.

2. A mechanical pipette comprising a cylindrical barrel, a nozzle-like tip plugged Yinto 'and closing one end of said barrel, said tip having a longitudinal bore -constituting a passage and also a container -for a predetermined .quantity of liquid, a bushing -adjustably mounted in the opposite end of said bar-rel, `a plunger operable in said barrel,.said plunger having an enlarged portion mounted for reciprocation in said Ibushing and projecting beyond `the outer end'of said bush- 4 ing and being provided with a lngerpiece, finger grips rigidly mounted on said barrel, the bore of said nozzle being relatively restricted in cross section and being linearly straight from end to end, said plunger having a reduced portion tting snugly and being slidably mounted in the bore of said nozzle and constituting a piston, said bushing .constituting an adjustable stop device for said plunger, Ithe portion of the yplunger within said barrel being provided with a shoulder which -is cooperable with said bushing, and spring means surrounding that portion of the plunger in said barrel, said spring means bearing at one end :against said tip and at its opposite end against :said stop shoulder.

3. A mechanical pipette for taking milk samples for testing purposes comprising a barrel open and internally screw threaded at opposite ends, said barrel being provided at one end with outstanding nger-grips, a screw-threaded bushing adjustably screwed y'into said one end, ,a screwthreadedxcentrally bored nozzle-tip Ascrewed into the opposite end lof said barrel, the bore in said nozzle-tip being relatively restricted and linearly straight from end to end and constituting .a milk receiving and storing chamber of predetermined and limited capacity and being adapted to permit a .limited amount of milk to be sucked into same and subsequently discharged on a microscopic slide for testing purposes, a plunger including a relatively large rod portion slidable in said bushing, `said rod portion having a shoulder abutting said bushing so that the bushing and shoulder portion ofthe plunger may be adjusted in respect to the barrel, said plunger also including a reduced rod constituting a piston and vfitting land operating snugly in the bore in ysaid nozzle rtip, that portion of said nozzle tip which extends into the bore of the barrel being reduced in cross :section and formed into a stuffing box, and thereduced rod portion being .operable in saidstu'ng box.

GEORGE S. RIGGS.

REFERENCES CITED The following references are of record in the le -of this patent:

UNITED STATES .PATENTS Number Name Date 404,105 Overlach May 28, 1889 '730,065 Wilson June '2, 1903 928,351 Wilkinson July 20, 1909 1,361,943 Westfall Dec. 14, 1920 1,521,822 Manzell Jan. 6, 1925 :2,129,675 Cole Sept. '13, v1938 '2,218,253 Ellsworth .Mar. 31, 1942 

